Ruggedized electric discharge device structure



June 5, 1962 R. J. NEY 3,038,094

RUGGEDIZED ELECTRIC DISCHARGE DEVICE STRUCTURE Filed Nov. 10, 1958 2Sheets-Sheet 1 lNVENTOR: ROBERT J. NEY,

H S ATTO R N EY.

June 5, 1962 R. J. NEY 3,038,094

RUGGEDIZED ELECTRIC DISCHARGE DEVICE STRUCTURE Filed Nov. 10, 1958 2Sheets-Sheet z INVENTOR: ROBERT J. NEY,

NWT-

HIS ATTORNEY.

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' Patentedlune 1952 My invention relates to electric discharge devicesand pertains more particularly to an improved television camera tubeconstruction including improved means for rigidly mounting electrodeassemblies therein.

When television camera tubes, such as those known as image orthicons,are employed, for example, in vibrating vehicles the vibration andresultant relative movement of electrode elements therein tend to affectadversely the picture quality. For example, in such tubes a photocathodeis generally mounted on the internal surface of a faceplate comprisingan end wall of the envelope and an electron gun mounted in the oppositeend of the tube directs an impinging electron beam on a target electrodewhich is mounted in the envelope intermediate the gun and photocathodeand adjacent the latter for cooperating electrically therewith. In thisarrangement the electron gun includes a very small axially disposedaperture for defining the beam and any substantially excursion of thegun aperture fromthe axis of the envelope, due to vibration of the gun,or movement of the target electrode, due to vibration of the assembly inwhich it is mounted, results in relative movements between theseelements and between these elements and the photocathode mounted on theenvelope. Such relative movements tend to introduce microphonicinterference or subtract from picture quality. Further, electricalconnections are generally made to the various electrodes in the tubethrough conductive leads extending through and sealed in the wall of thetube envelope and substantial vibratory movement of the electrodes tendsto fatigue and fracture the leads.

Heretofore, electrode vibration in camera tubes has been clamped by useof a plurality of compressed cantilever snubbers or spring clips spacedcircumferentially completely about the electrode assemblies andyieldably engaging the inner walls of the tube envelope. This type ofdamping means has proved adequate, for example, in studio televisioncamera use where vibration is relatively slight. However, such mountingmeans have not proved adequate where the cameras are used in movingvehicles or other equipment subject to high vibration. Under operatingconditions of the latter type and with tubes employing the mentionedprior art damping means, all of the above-discussed adverse effects aregenerally encountered.

Accordingly, a primary object of my invention is to provide a new andimproved television camera tube construction including new and improvedmeans for minimizing microphonic interference under highly vibratoryconditions of operation.

Another object of my invention is to provide a new and improved meansfor increasing the natural frequency of electrode assemblies in electricdischarge devices for thus minimizing vibratory movements of suchassemblies.

Another object of my invention is to provide a new and improved meansfor mounting electrode assemblies in television camera tubes morerigidly in respect to the tube envelopes.

Another object of my invention is to provide new and improved means formore effectively maintaining an electron beam source coaxially alignedin an electric discharge device envelope.

Another object of my invention is to provide new and improved means fordecreasing relative movements between an electron gun and targetelectrode assemblies v mounted in the envelope of a tube and betweenthese assemblies and a photocathode mounted on a wall portion of a tubeenvelope containing these assemblies.

Another object of my invention is to provide new and improved means forminimizing failure of tube com ponents resulting from fatigue due toexcessive vibratory movements of elements mounted in the tube.

Further objects and advantages of my invention will become apparent asthe following description proceeds 0 and the features of novelty whichcharacterize my invention will be pointed out with particularity in theclaims annexed to and forming part of this specification.

In carrying out the objects of my invention I provide an electricdischarge device of the camera tube type including an insulativeenvelope having a photocathode on an end wall and containing an electrongun-dynode assembly in the opposite end of the envelope and aninterpositioned image section assembly including a target electrode. Theelectrode assemblies are each mounted rigidly in the envelope byradially extending high spring constant elements which rigidly engagethe wall of the envelope on one side of the assemblies and radiallyextending elements of lower spring constants which are under compressionand yieldably engage the envelope wall on the sides opposite the rigidelements. In the electron gun-dynode assembly, support rings carry the,radially extending elements and a low-mass support arrangement in onering provides a single-end support for. the gun of the assembly.

For a better understanding of my invention reference may be had to theaccompanying drawing in which:

FIGURE 1 is a somewhat schematic side elevational view of a televisioncamera tube of the image orthicon type in which my invention isincorporated;

FIGURE 2 is an enlarged fragmentary partially sectionalized view of theimage section of the device of FIGURE 1 wherein is illustrated one formof my improved mounting means;

FIGURE 3 is a sectional view taken along the line 3--3 in FIGURE 2;

FIGURE 4 is an enlarged fragmentary partially sectionalized view of themultiplier section of the device of FIGURE 1 illustrating certainfeatures of my invention in greater detail;

FIGURE 5 is a sectional view taken along the line 5-5 in FIGURE 4;

FIGURE 6 is an enlarged fragmentary partially sectionalized View of amodified form of my invention; and

FIGURE 7 is a sectional view taken along the line 7-7 in FIGURE 6.

Referring to FIGURE 1, there is shown therein my invention incorporatedin a camera tube of the image orthicon type and generally designated 1.The tube 1 comprises an insulative, and preferably glass, envelope 2including an enlarged head portion 3 and an elongated neck portion 4.The head portion houses the image section of the device while the neckportion houses both the multiplier and beam forming sections, all ofwhich will be described in greater detail hereinafter.

As perhaps better seen in FIGURE 2, the head portion 3 of the envelopeincludes a transparent faceplate 7 on the inner surface of which isprovided a suitable photocathode 8 which is included in the imagesection. Additionally, the image section includes a plurality ofcylindrical grid electrodes. These electrodes are mounted togethercoaxially and to comprise a unitary assembly 10 by being each suitablysecured to a plurality of circumferentially spaced insulative rods orstalks 11. The assembly 10 thus provided includes an accelerating grid12 for controlling the velocity of electrons moving away from thephotocathode and toward a target electrode assembly 13 mounted in asupport ring 14. The target electrode included in this assembly can beof the type disclosed and claimed in US. patent application Serial No.737,348 of Herbert J. Hannam filed May 23, l958, and assigned to thesame assignee as the present invention. The remaining electrode of theassembly 10 is a decelerator grid 15 for controlling the impinging forceof electrons striking the target from an electron beam source located inthe neck portion of the envelope. Extending through the back portion ofthe head 3 and sealed therein are a plurality of conductive leads 16which make electrical connections to the various electrodes included inthe image section 10.

Provided for holding the assembly 10 rigidly in place in the envelopehead is one form of my invention. This form is perhaps best seen inFIGURE 3 wherein each of the electrodes 12 and 15 is provided with apair of bumper extensions or elements 20 spaced approximately 90 degreesapart and a pair of elliptical spring clips 21 with each of the springclips 21 approximately diametrically oppoiste one of the bumper elements20.

The bumper elements 20 each comprise a generally U-shaped or bail-likestructure each end of which includes a foot portion 22 secured, as byspot welding, to its associated electrode. The bowed or bight portionsof the elements 20 rigidly engage the inner surface of the envelopeWall. Additionally, the elements 20 are constructed to be rigid or, thatis, to have a high spring constant which is preferably in the order ofthe spring constant of the glass envelope wall which it engages.

The spring clips 21 are also generally U-shaped or bail-like and eachhas a foot portion 23 secured, as by spot welding also, to theassociated electrode, and a bowed or bight portion in compression andyieldably engaging the wall of the envelope. The clips 21 each extendpartially about the circumference of its associated electrode with thefree end comprising a foot portion 24 in sliding engagement with theouter surface of the electrode. The spring clips 21 have a substantiallylower spring constant relative to those of the elements 20 and theenvelope Wall. I have found Inconel X and tungsten suitable materialsfrom which to form the spring clips 21. These materials are high yieldstrength materials at elevated temperatures and thus provide desiredspring characteristics even after bakeout of the tube. The manner inwhich the just-described arrangement including pposed envelope engagingelements of different spring constants is effective for minimizingelectrode vibrations will be described hereinafter in detail in a jointconsideration of this arrangement and a modified form employable with anelectron gun-dynode assembly 25 in the multiplier section of the tube.

As perhaps better seen in FIGURE 4, the electron gun-dynode assembly 25comprises an electron beam source in the form of an electron gun 26, aplurality of dynode elements 27, an anode 28 mounted between the lastand the penultimate dynode, a multiplier focusing grid 29 and a pair ofcup-shaped assembly supporting rings 30, with each of the latter mountedat an end of the assembly. These elements are all coaxially arranged andsuitably mounted in insulated longitudinally spaced relation by beingsuitably secured to a plurality of circumferentially spaced insulativerods or stalks '31. A plurality of leads 32 are sealed through the endof the tube envelope with the inner ends connected, as by welding, toelectrode elements in the assembly 25 and the outer ends suitablyconnected to separate prongs 33 carried in an insulative base 34.

The electron gun 26 comprises a tubular element containing an emitter(not shown) and carrying at one end a disk 35 including an aperture 36aligned coaxially in the envelope. The end of the gun 26 opposite thedisk 35 is fitted in an elongated cylindrical collar 37 formed centrallyon the rear support ring 3%. A space between the collar 38 and the gunis filled with a quantity of solder material 39. A ring 40 is fitted inthe support ring 3!) with the outer edge secured to the cylindrical wallor rim of the ring 30 and the inner edge secured to the collar 38. Thisarrangement provides a low-mass rigid mount for the gun 26.

The disk aperture 36 of the gun is approximately l/500 of an inch indiameter and directs a thin beam of electrons toward the targetelectrode. Focusing of the beam is effected by a cylindrical gridcomprising a coating of conductive material 37 on the inner wall of thescanning section 3 of the tube neck, and by an axial magnetic fieldsupplied -by magnetic means not shown; and the focused beam is effectivefor producing a spot size of approximately 1 to 2 mils on the targetelectrode. In operation, suitable deflection means (also not shown) areprovided to scan the target with the beam and the beam surrenderselectrons to the target electrode in accordance with charges onincremental portions thereof determined by the photocathode; and theremaining electrons of the beam are returned to the gun to provide anelectrondeficiency signal. However, the returning electrons do notfollow the same path as those approaching the target due to slight fielddistortions. As a result, the returning electrons normally do notre-enter the aperture 36. Instead, these electrons land on the disk 35,which serves as the first dynode, and cause secondary electrons to beejected from the disk. The other dynodes are electronpermeable and thesecondary electrons ejected from the disk 35 cascade through thesucceeding dynodes, thus to effect a plurality of stages of electronmultiplication before leaving the tube via the anode 28 and as anamplified video signal.

It will be seen from the foregoing that the photocathode, by beingmounted directly on the inner surface of the faceplate 7, is rigidlymounted in the envelope and that any lateral movement of the electrongun relative to the envelope will move the aperture 36 out of alignmentwith the tube axis and thus distort the beam direction, and move thepoint of origin of the beam relative to the photocathode, causingmicrophonic interference tending adversely to affect the picturequality. The extent of such interference possible in prior art deviceswill be better understood from the fact that in such prior art devicesand under conditions of 10 g.s of acceleration the aperture 36 can movein the order of 60 mils out of alignment. This will result in a 60 milline impinging on the target rather than the desired 1 to 2 mil spot.Such a condition results in smearing of the image or a considerable dropin resolution. Additionally, excessive relative movement of theelectrode assemblies tends to fatigue and fracture the leads 16 and 32extending through the envelope wall and connected to the assemblies.

My improved structure is adapted for minimizing vibratory movement ofthe elements comprising the electron gun-dynode assembly and toaccomplish this the latter assembly is constructed to include a pair ofrelatively rigid snubber bars or extensions 40 secured to each of thesupport rings 30. The bars 41 of each pair are circumferentially spacedapproximately degrees apart and extend radially straight andperpendicularly engage the wall of the envelope neck. Also secured toeach support ring 30 are a pair of elliptical spring clips 42 which canbe identical in material, structure and function to those designated 21of the image section assembly and shown in FIGURES 1-3. The spring clips41 are each located diametrically opposite one of the bars 40 andinclude elongated bent portions which extend tangentially of theenvelope and which are compressed and yieldably engage the wall of theenvelope neck. In this arrangement the bars 41, like the bumper elements20 of the image section electrode assembly, have high spring constantsand the spring clips 42, like the spring clips 21, in the previouslydescribed section, have substantially lower spring constants.Additionally, the spring clips 42 are provided with an initialcompression or, in other words, are compressed by insertion of theassembly in the tube envelope.

The bars 41 provide substantially high rigidity. However, if desired,bumper elements of the type designated 20 in FIGURES 1-3 can besubstituted therefor.

Illustrated in FIGURES 6 and 7 is a modified form of my arrangement forrigidly mounting an electron gundynode assembly which can be identicalto that of FIG- URES 4 and except for the type of spring clips employed;In the presently considered structure the spring clips 4-2 arecantilever and comprise elongated bent portions which extendlongitudinally in the envelope and are compressed for yieldably engagingthe wall of the envelope neck. The material of the cantilever springclips 43 can be the same as that of the previously described ellipticalspring clips.

:In my improved structure the elements 20 and 41 preferably areconstructed to have spring constants comparable to that of the glassenvelope Wall and the support rings 30 and essentially govern thenatural frequency of the system. In fact, up to a certain value ofdynamic loading which can be designed to be above that to be experiencedby the tube under the worst vibratory conditions contemplated, theelements 20 and 41 act as if they were integral parts of the envelope.For example, I have with my structure been able to increase the naturalfrequency of the elements approximately 10 to times higher than thehighest impressed frequency for thereby minimizing undesirable electrodedeflection. Thus, my improved arrangement serves effectively to hold theelectrode assemblies 10 and 2-5 in as rigidly fixed positions in theenvelope as would support structure sealed into the glass wall of theenvelope. It does not, however, involve the shortcomings of sealed-insupport structures such, for example, as difficulties resulting fromdifferences in thermal expansion between materials, the making ofglass-to-rnetal seals about the supports, and the generally substantialdifliculties encountered in sealing structures in a fixed position in aglass envelope. Instead, my improved structure affords relatively simpleassembly involving merely insertion of the electrodes in the envelope.The high spring constant straight extensions and 51 rigidly abut theglass wall of the envelope, and the yieldalble spring clips 2 1, 42, and43 hold these extensions 20 and 41 in rigid abutment with the glass wallwhile serving also to accommodate differences in expansion between theglass and metal parts of the electrode assemblies. Thus, my structure iseffective for rigidly mounting electrode assemblies in a tube envelopeand, in camera tubes, is effective for maintaining the electrongun-dynode assembly so positioned as to minimize to a negligible amountany excursion of the gun aperture 36 which would adversely affectpicture quality due to microphonic interferences. Also, it is effectivefor minimizing microphonic interferences due to vibratory movements ofthe electrode assemblies, including the radial motion of the targetelectrode, in the image section of the tube.

In making comparison tests between my structure and image orthiconcamera tubes employing prior mounting means, and specifically springclips located at 90 degree intervals completely about the electron gunstructure, I have submitted both types of structure to impressed maximumaccelerations of 10 gs. The prior art structure was found .to have 2major resonant frequencies, in the range of 5 to 500 cycles per second(c.p.s.). The resonant condition occurred at 140 to 20% c.p.s. and 310to 340 c.p.s., respectively, with the result that the double amplitudeof the gun aperture at resonance were 35 to 58 mils and to 32 mils,respectively. As pointed out above, such excursions of the gun aperturegenerally result in comparable excursions of the beam on the targetelectrode and, inasmuch as the spot size to be scanned on the targetelectrode is in the order of only 1 to 2 mils, the gun apertureexcursions result in substantial smearing of the picture or asubstantial drop in image resolution. It will be seen that anysubstantial lateral movement of the target electrode relative to thebeam would have the same undesir able effect.

In contrast, my improved electrode mounting structure maintains thevarious electrode assemblies each substantially rigid relative to theenvelope and, thus, to each other. In testing tubes including electrodesmounted according to my invention and in subjecting such tubes to thesame vibratory conditions as the above-discussed prior art structure, Iobserved a marked absence of resonant frequencies over the specifiedrange of 5 to 500 c.p.s. and the maximum deflection observed was onlyabout 2 mils. Thus, my structure has been found particularly effectivefor avoiding picture smearing or poor image resolution due tomicrophonic interference or undesirable effects due to the relativemovement of the electrodes in the device. The reduced movement of theelectrode assemblies is also effective for minimizing fatiguing of theconductive leads extending through the envelope and, thus, is effectivefor prolonging the lives thereof.

It will be understood from the foregoing that while I have shown myinvention applied to a camera tube it is equally applicable to any tubeconstruction wherein it is desirable to mount rigidly electrode means inan envelope construction. Additionally, it is to be understood from theforegoing that in some applications the different types of extensions 20and 41 can be interchangeably or alternatively employed as can thedifferent types of spring clips 21, 42 and 43. I have found, however,that the elliptical type of spring elements are particularly adaptablein devices which are ordinarily subjected to elevated temperatures inprocessing. This type of element does not have to be stressed near itselastic limit, as do some cantilever springs, to be effective. Thus,when heated, as during bakeout, the elliptical springs do not tend toyield plasticly or to lose any appreciable portion of their springconstant.

While I have shown and described specific embodiments of my invention Ido not desire my invention to be limited to the particular forms shownand described, and I intend by the appended claims to cover allmodifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An electric discharge device comprising an envelope, an electrodeassembly contained generally coaxially in said envelope, and means forrigidly mounting said assembly in said envelope including a first pairof circumferentially spaced rigid bail-like elements each extending in adirec tion transverse the axis of said envelope and having both endsthereof secured to said electrode assembly, said first pair of bail-likeelements having a spring constant comparable to that of said envelopeand rigidly engaging the wall of said envelope, and a second pair ofbail-like elements each diametrically disposed relative to one of saidfirst pair of elements and each extending in a direction transverse theaxis of said envelope and having one end secured to said electrodeassembly with the other slideably engaging same, said second pair ofelements being under compression and having a substantially lower springconstant than said first pair of elements and yieldably engaging saidenvelope wall for maintaining said first pair of elements in saidengagement with the wall of said envelope.

2. An electric discharge device comprising an envelope, an electrodeassembly contained generally coaxially in said envelope, and means forrigidly mounting said assembly in said envelope including a pair ofcircumferentially spaced rigid bail-like elements each extendingradially from said electrode assembly, said bail-like elements havingbight portions conforming to and making substantial surface contact withthe inner surface of said envelope, having a spring constant comparableto that of said envelope and rigidly engaging the wall of said envelope,and a pair of elliptical spring elements each diametrically disposedrelative to one of said bail-like elements and each 7 extending in adirection transverse the axis of said envelope and having one endsecured to said electrode assembly with the other slideably engagingsame, said spring elements being under compression and having a lowerspring constant than said bail-like elements and yieldably engaging saidenvelope wall.

3. An electric discharge device comprising an envelope, an electrodeassembly contained generally coaxially in said envelope, and means forrigidly mounting said assembly in said envelope including a pair ofcircumferentially spaced rigid rod-like elements extending radially fromsaid electrode assembly, said rod-like elements having a spring constantcomparable to that of said envelope and having the ends thereof abuttingthe wall of said envelope, and a pair of cantilever spring elements eachhaving an end secured to said electrode assembly diametrically oppositeone end of said rod-like elements and extending coextensively with theaxis of said electrode assembly, said spring elements being compressedand having a lower spring constant than said rod-like elements andyieldably engaging said envelope wall.

4. An electric discharge device comprising an elongated envelope, anelectrode assembly including an electron gun having an aperture at oneend thereof and coaxial with the longitudinal axis of said envelope anda coaxial gun support ring having said gun rigidly mounted centrallytherein and extending transversely in said envelope, and a pair ofrod-like elements spaced approximately 90 degrees apart and secured toand extending radially from said ring, said rod-like elements beingrigid and having the ends thereof abutting the wall of said envelope,and a pair of spring elements each diametrically opposite one of saidrod-like elements and having a spring constant lower than that of saidrod-like elements, said spring elements being compressed and yieldablyengaging said envelope Wall for maintaining said rod-like elements inabutting relation with the opposite Wall of said envelope, wherebyexcursion of said gun aperture out of said coaxial position undervibratory conditions is minimized.

5. A device according to claim 4, wherein said support ring includes aconcentric outer rim and a central collar, said gun includes a tubularmember positioned in and bonded to said collar, and a ring is secured insaid support ring between said rim and collar for thereby providing alow-mass rigid mount for said gun.

6. A television camera tube comprising an elongated envelope, a unitaryelectrode assembly in said envelope including a plurality of coaxiallongitudinally spaced electrodes and a centrally extending electron gunhaving a coaxially disposed electron aperture, said assembly beingsupported between a pair of longitudinally spaced coaxial support ringsextending transversely in said envelope, a plurality of conductive leadsextending through a base portion of said envelope and connected to saidelectrodes and gun, a pair of circumferentially spaced rigid radialextensions on each of said support rings engaging the wall of saidenvelope, and another pair of extensions on the diametrically oppositeside of each of said rings, said last-mentioned extensions having asubstantially lower spring constant relative to the other extensions andyieldably engaging the wall of said envelope, whereby excursions of saidgun aperture out of said coaxial position and stresses on said leadsunder vibratory conditions of said tube are minimized.

7. A television camera tube comprising an elongated envelope, a unitaryelectrode assembly in said envelope including a plurality of coaxiallongitudinally spaced tubular grids and a transverse target electrode, apair of circiunferentially spaced rigid radial extensions on each ofsaid grids engaging the wall of said envelope, a plurality of leadsextending through the wall of said envelope and making electricalconnections to said assembly, and another pair of extensions on thediametrically opposite side of each of said grids, said last-mentionedextensions having a substantially lower spring constant relative to theother extensions and yieldably engaging the wall of said envelope formaintaining said first-mentioned radial extensions in engagement withthe wall of said envelope, whereby movements of said assembly relativeto said envelope and stresses in said leads under vibratory conditionsof said tube are minimized.

8. An image orthicon comprising an elongated envelope including anelongated neck portion and an enlarged head portion, a photocathodemounted on the transverse end wall of said head portion, a unitaryelectrode assembly contained in said neck portion and including aplurality of coaxially longitudinally spaced dynodes and a centrallyextending electron gun having a coaxially disposed electron aperture,said assembly being supported between a pair of longitudinally spacedcoaxial support rings extending transversely in said envelope, aplurality of conductive leads sealed in the end of said neck portion ofsaid envelope and connected to said dynodes and gun, a unitary imageassembly contained in said head portion of said envelope and including apair of coaxial longitudinally spaced tubular grids, a transverse targetelectrode interposed between said photocathode and gun and a pluralityof leads sealed in said envelope head portion and connected to saidimage assembly, a pair of rigid extensions spaced approximately degreesapart and secured to and extending radially from each of said supportrings and said tubular grids, said extensions having a spring constantcomparable to that of said envelope wall and abutting said wall, and apair of radial extensions diametrically opposite each of saidfirst-mentioned pairs of extensions having a spring constant lower thanthat of said first-mentioned extensions, said last-mentioned extensionsbeing normally under compression and yieldably engaging the wall of saidenvelope, whereby movements of said assemblies out of said coaxialpositions and stresses in said leads under vibratory conditions of saidtube are minimized.

9. An electric discharge device comprising an envelope, an electrodeassembly contained in said envelope, and means for mounting saidassembly in said envelope in a manner to afford an extremely highresonant frequency under vibratory conditions of said device including aplurality of circumferentially spaced radial extensions on saidassembly, the extensions on one side of said assembly constituting apair of rigid members each having a substantial surface portionconforming to and abutting the inner surface of the wall of saidenvelope, said lastmentioned extensions being of predetermined lengthsfor accurately positioning said assembly relative to said envelope, andthe extensions on the opposite side constituting a pair of springs undercompression and engaging said envelope wall for maintaining said rigidextensions in said abutment with said envelope wall under vibratoryconditions.

References Qited in the file of this patent UNITED STATES PATENTS2,452,620 Weimer Nov. 2, 1948 2,542,108 Bayford et al Feb. 20, 19512,598,919 Jensen June 3, 1952 2,658,161 DeAno Nov. 3, 1953 2,755,405Wilhelm July 17, 1956 2,847,599 Kasernan Aug. 12, 1958 2,897,389 SalgoJuly 28, 1959 FOREIGN PATENTS 787,721 Great Britain Dec. 11, 1957

